diff --git a/llt/utf8.c b/llt/utf8.c
index fee04ba..b8b0456 100644
--- a/llt/utf8.c
+++ b/llt/utf8.c
@@ -12,6 +12,7 @@
   valid.
   A UTF-8 validation routine is included.
 */
+#define _XOPEN_SOURCE 700
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
diff --git a/llt/utf8.h b/llt/utf8.h
index af6b5cb..ea0142a 100644
--- a/llt/utf8.h
+++ b/llt/utf8.h
@@ -16,7 +16,7 @@ typedef unsigned long long u_int64_t;
 
 extern int locale_is_utf8;
 
-#if defined(__WIN32__) || defined(__linux__)
+#if defined(__WIN32__)
 extern int wcwidth(uint32_t);
 #endif